This invention pertains to universal joints and more particularly to low cost universal joints which couple together a pair of intersecting shaft portions or the like.
Universal joints commonly include a pair of intersecting pins which extend through aligned openings in the forks and in the block or cube. One common method of making such universal joints consists of the use of intersecting pins, one of which is larger in diameter than the other. The larger diameter pin, known as the main pin, extends between its forks with its extreme ends generally flush with the outer surfaces of the forks, and is provided with a central transverse opening therethrough. A second pin of smaller diameter, also known as a cross pin, extends at right angle through the opening in the main pin and through aligned openings in the other pair of forks. Such cross pin has commonly been fabricated to a length somewhat greater than the spaced apart distances of the forks through which it extends, so that a portion thereof protrudes above each of its forks. The exposed ends of the cross pins are then peened over and flattened to retain the cross pin in place. In U.S. Pat. Nos. 1,806,723 of 1931 and 2,153,415 of 1939, the cross pin is formed flush with the forks and is grooved to receive a snap ring or a keeper wire which locks the cross pin in place.
Such universal joints have an advantage of being relatively low in cost and easy to manufacture. However, they have certain distinct disadvantages. First, the cross pin has exposed heads on the surfaces of the forks which may be undesirable. Further, since the cross pin is captured at the forks, the relative rotation does not take place at the forks but rather takes place between the cross pin and the block at a region spaced substantially inwardly of the ends of the cross pin. When the universal joint is subjected to rotational torque, far greater unit bearing pressures are thus exerted on the cross pin, as compared to the main pin, because of the relatively shorter radius through which the bearing forces are transmitted. Since the cross pin is smaller, it is thus subject to earlier wear and failure.
Further, it has been common to provide an axial opening through the main pin leading to the region of intersection thereof to provide for access of lubricating fluids so that the cross pin and block may be lubricated. This increases the cost of the joint.
A further disadvantage results in the fact that the cross pin must be sufficiently malleable to be peened over, and something under 40 Rockwell C Scale is required. Even then substantial work hardening can result at the heads of the cross pin.